const base64map =
  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

// Crypto cryptoUtilities
export const cryptoUtil = {
  // Bit-wise rotate left
  rotl: function (n, b) {
    return (n << b) | (n >>> (32 - b));
  },

  // Bit-wise rotate right
  rotr: function (n, b) {
    return (n << (32 - b)) | (n >>> b);
  },

  // Swap big-endian to little-endian and vice versa
  endian: function (n) {
    // If number given, swap endian
    if (n.constructor == Number) {
      return (
        (cryptoUtil.rotl(n, 8) & 0x00ff00ff) |
        (cryptoUtil.rotl(n, 24) & 0xff00ff00)
      );
    }

    // Else, assume array and swap all items
    for (var i = 0; i < n.length; i++) n[i] = cryptoUtil.endian(n[i]);
    return n;
  },

  // Generate an array of any length of random bytes
  randomBytes: function (n) {
    for (var bytes = []; n > 0; n--)
      bytes.push(Math.floor(Math.random() * 256));
    return bytes;
  },

  // Convert a string to a byte array
  stringToBytes: function (str) {
    var bytes = [];
    for (var i = 0; i < str.length; i++) bytes.push(str.charCodeAt(i));
    return bytes;
  },

  // Convert a byte array to a string
  bytesToString: function (bytes) {
    var str = [];
    for (var i = 0; i < bytes.length; i++)
      str.push(String.fromCharCode(bytes[i]));
    return str.join("");
  },

  // Convert a string to big-endian 32-bit words
  stringToWords: function (str) {
    var words = [];
    for (var c = 0, b = 0; c < str.length; c++, b += 8)
      words[b >>> 5] |= str.charCodeAt(c) << (24 - (b % 32));
    return words;
  },

  // Convert a byte array to big-endian 32-bits words
  bytesToWords: function (bytes) {
    var words = [];
    for (var i = 0, b = 0; i < bytes.length; i++, b += 8)
      words[b >>> 5] |= bytes[i] << (24 - (b % 32));
    return words;
  },

  // Convert big-endian 32-bit words to a byte array
  wordsToBytes: function (words) {
    var bytes = [];
    for (var b = 0; b < words.length * 32; b += 8)
      bytes.push((words[b >>> 5] >>> (24 - (b % 32))) & 0xff);
    return bytes;
  },

  // Convert a byte array to a hex string
  bytesToHex: function (bytes) {
    var hex = [];
    for (var i = 0; i < bytes.length; i++) {
      hex.push((bytes[i] >>> 4).toString(16));
      hex.push((bytes[i] & 0xf).toString(16));
    }
    return hex.join("");
  },

  // Convert a hex string to a byte array
  hexToBytes: function (hex) {
    var bytes = [];
    for (var c = 0; c < hex.length; c += 2)
      bytes.push(parseInt(hex.substr(c, 2), 16));
    return bytes;
  },

  // Convert a byte array to a base-64 string
  bytesToBase64: function (bytes) {
    // Use browser-native function if it exists
    if (typeof btoa == "function") return btoa(cryptoUtil.bytesToString(bytes));

    var base64 = [],
      overflow;

    for (var i = 0; i < bytes.length; i++) {
      switch (i % 3) {
        case 0:
          base64.push(base64map.charAt(bytes[i] >>> 2));
          overflow = (bytes[i] & 0x3) << 4;
          break;
        case 1:
          base64.push(base64map.charAt(overflow | (bytes[i] >>> 4)));
          overflow = (bytes[i] & 0xf) << 2;
          break;
        case 2:
          base64.push(base64map.charAt(overflow | (bytes[i] >>> 6)));
          base64.push(base64map.charAt(bytes[i] & 0x3f));
          overflow = -1;
      }
    }

    // Encode overflow bits, if there are any
    if (overflow != undefined && overflow != -1)
      base64.push(base64map.charAt(overflow));

    // Add padding
    while (base64.length % 4 != 0) base64.push("=");

    return base64.join("");
  },

  // Convert a base-64 string to a byte array
  base64ToBytes: function (base64) {
    // Use browser-native function if it exists
    if (typeof atob == "function")
      return cryptoUtil.stringToBytes(atob(base64));

    // Remove non-base-64 characters
    base64 = base64.replace(/[^A-Z0-9+\/]/gi, "");

    var bytes = [];

    for (var i = 0; i < base64.length; i++) {
      switch (i % 4) {
        case 1:
          bytes.push(
            (base64map.indexOf(base64.charAt(i - 1)) << 2) |
              (base64map.indexOf(base64.charAt(i)) >>> 4)
          );
          break;
        case 2:
          bytes.push(
            ((base64map.indexOf(base64.charAt(i - 1)) & 0xf) << 4) |
              (base64map.indexOf(base64.charAt(i)) >>> 2)
          );
          break;
        case 3:
          bytes.push(
            ((base64map.indexOf(base64.charAt(i - 1)) & 0x3) << 6) |
              base64map.indexOf(base64.charAt(i))
          );
          break;
      }
    }

    return bytes;
  },
};
